Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$143.88	5.373%	$151.6107	$151.61	$151.60	$151.60
Purchase #2	$105.71	12.538%	$118.9639	$118.96	$118.95	$119.00
Purchase #3	$78.75	9.696%	$86.3856	$86.39	$86.40	$86.40
Purchase #4	$209.76	9.511%	$229.7103	$229.71	$229.70	$229.70
Purchase #5	$81.79	4.258%	$85.2726	$85.27	$85.25	$85.30
Purchase #6	$197.57	11.511%	$220.3123	$220.31	$220.30	$220.30
Purchase #7	$76.63	7.488%	$82.3681	$82.37	$82.35	$82.40
7 purchase totals =	$894.09		$974.6235	$974.62	$974.55	$974.70